1. Field of the Invention
The present invention relates broadly to the production of oil from subsurface geological formations. More particularly, the present invention relates to methods and apparatus for real time control of oil exploitation through active intervention in the process of the oil reservoir exploitation.
2. State of the Art
It is well recognized in the art that the monitoring of fluid movement in subsurface formations is essential in improving oil recovery techniques. Only by monitoring the reservoir is it possible to intervene in the recovery process in order to maximize recovery.
For many years, monitoring was carried out via the periodic logging of cased wells. More recently, monitoring has evolved into the continuous monitoring of pressure, temperature, and flow rates within the wellbore (See, e.g., Baker et al., "Permanent Monitoring," Oilfield Review, 7(4) 32-46 (1995)). Such continuous acquisition of data, when properly analyzed, has had the benefit of reducing production loss, because the analysis of the data has led to occasional intervention in the recovery process.
For example, decisions regarding oil production are presently most often based on decline curve analysis. (See, A. Satter and G. Thakur, Integrated Petroleum Reservoir Management, A Team Approach, Pennwell Publishing Company, Chapter 6 (1994). A detailed analysis is often carried out using standard reservoir simulators where factors such as optimal production/injection well placement are studied. Using history matching technique, an update to the reservoir model is carried out. Reservoir simulation is then complemented with results from data obtained from the well. As a result, determinations are made as whether to intervene in the recovery process (e.g., in order to increase production) such as by using an acid treatment, a fracture job, infill drilling, or the drilling of new wells to produce unswept oil. (See, Integrated Petroleum Reservoir Management, id.)
While the present techniques of monitoring and occasional intervention in the production process are useful in increasing production and reducing costs, these techniques are not ideal because they do not control the reservoir production in the shortest time scale of practical relevance ("real time"), but rather are reactive in nature to conditions that may have changed over a long period of time.